Traditionally, an instance of operating system (OS) installation is associated exclusively with an individual computing device. Thus, any specializations for a given OS installation may be made for the particular hardware of the individual computing device without regard to separate installations on different systems and platforms. Some modern operating systems, though, enable features to migrate an instance of operating system installation to different machines at different times by way of portable storage devices, network-accessible storage and/or other storage. Traditional techniques to handle specialization for a single machine configuration do not provide mechanisms that are suitable for booting of a portable OS installation across different machines that may have different hardware configurations.